This invention relates to medical implants containing magnetic material placed around a tissue or body structure, where the medical implant can be made more compatible with competing magnetic fields, such as those present during Magnetic Resonance Imaging (MRI), by employing “floating” magnets.
Strong magnetic fields such as those within an MRI scanner can cause magnetic material in a medical implant to depolarize or repolarize, and also can induce undesirable forces on the medical implant. The magnetic field may induce a torsional force that attempts to align the magnetic poles within the implant to the magnetic field. This force can result in undesirable stress on the patient's body tissues, or on the implant itself. If the magnetic field is of sufficient strength, and the magnets in the implant cannot move to align themselves with the magnetic field, the magnetic field can cause the magnetic poles of some or all of the magnets in the implant to reorient (repolarize) to align with the magnetic field. If the poles of some magnetic elements within a medical implant reorient and some do not, resulting in poles not all in the same orientation, the unaligned poles could neutralize each other and cause a loss or reduction of magnetism (depolarization). This may result in the implant functioning poorly or not at all even after the magnetic field is removed (e.g., after the MRI scan is complete).